1. Field of the Invention
This invention relates to industrial heating ovens. In one of its aspects, the invention relates to an industrial drying oven for painted work and the like wherein energy required for circulating air through the furnace is minimized.
2. State of the Prior Art
Recent increases in fuel costs and projected scarcity of fuel have greatly increased the interest in energy conservation in industrial processes. For example, in fume incineration, the heat of incineration has been recovered and used for preheating the fume containing feed to the incinerator. Further, the heat of incineration has been recovered and used to heat these fumes for recycling solvent containing gases to the furnace. See Gentry U.S. Pat. No. 3,706,445 issued Dec. 19, 1972, and Hardison et al U.S. Pat. No. 3,484,189 issued Dec. 16, 1969.
It has recently been suggested to make a rotary generator or heat exchanger wheel from a thermally stable ceramic material sold under the mark CER-VIT.RTM. and to use such a regenerator in an industrial incineration process. For example, see Gentry U.S. Pat. No. 3,442,953 issued Mar. 9, 1976. In one prior art system wherein the exhaust from the incinerator is heat exchanged in a ceramic wheel with fume-laden gases from a drying oven as disclosed and claimed in the Gentry U.S. Pat. No. 3,442,953, the exhaust from the heat exchanger has been further heat exchanged with air in metal heat exchange wheels to heat process air for the drying oven.
The heat in the exhaust from an industrial heating furnace is heat exchanged with combustion air in a shell and tube heat exchanger in the disclosure in the U.S. Pat. Nos. to Bradshaw, 1,476,142, issued Dec. 4, 1973, and Hanley Jr., 1,658,332, issued Feb. 7, 1928. The shell and tube heat exchangers are very expensive to construct, are very large and very heavy. Furthermore, these heat exchangers are relatively inefficient in that the heat must pass through thick metal tubes. In Hanley, a fan is provided upstream of the heat exchanger to blow the air therethrough and a second fan is provided on the downstream side of the heat exchanger to draw the exhaust gases therethrough.
In Holbeck U.S. Pat. No. 1,590,373 issued June 29, 1976, recuperation of heat from an open hearth furnace is provided by heat exchanging makeup air for combustion with the exhaust gases from the furnace. Rotating metal discs are provided for this purpose.
In the U.S. Pat. No. 3,837,794 to Phillips issued Sept. 24, 1974, there is disclosed and claimed a billet heating furnace having a plurality of turbulating pipes in a preheating zone. The turbulating pipes are supplied with the air under pressure and have a plurality of jet nozzle openings therealong to uniformly direct the gases against the articles throughout the length of the preheating section to increase the heat transferability of the heated gases in the preheat section of the furnace.